#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{
	int n;
	while (~scanf("%d", &n)) {
		int num1 = 1, num2 = 1, ret = 0;
		for (int i = 2; i < n; i++) {
			ret = num1 + num2;
			num1 = num2;
			num2 = ret;
		}
		printf("%d\n", ret);
	}
	return 0;
}